BRUSSELS (Reuters) -Apple, Alphabet's Google and Meta Platforms will be investigated for potential breaches of the Digital Markets Act, EU antitrust regulators said on Monday, a move that could lead to hefty fines for the companies.

The law, effective from March 7, requires six gatekeepers - which provide services like search engines, social networks and chat apps used by other businesses - to comply with guidance to ensure a level playing field for their rivals and to give users more choices.

"The (European) Commission suspects that the measures put in place by these gatekeepers fall short of effective compliance of their obligations under the DMA," the EU executive said in a statement.

The EU competition enforcer will investigate Alphabet's rules on steering in Google Play and self-preferencing on Google Search, Apple's rules on steering in the App Store and the choice screen for Safari and Meta's 'pay or consent model'.

The Commission is also taking steps to investigate Apple's new fee structure for alternative app stores and Amazon's ranking practices on its marketplace.

The EU executive aims to wrap up the investigations within a year, the timeframe set out under the DMA.